Particle advancing apparatus



March 17, 1959 L. A. CARLSMITH ET AL 2,

' PARTICLE ADVANCING APPARATUS Filed Jan. 26, 1956 I 2 Sheets-Sheet 1 [F l G. i

March 1959 L. A. CARLSMITH ETAL 2,

PARTICLE ADVANCING APPARATUS 2 Sheets-Sheet 2 Filed Jan. 26, 1956 United States Patent PARTICLE ADVANCING APPARATUS Lawrence A. Carlsmith, Amherst, and John P. Rich, Nashua, N. H., assignors to Improved Machinery, Inc., Nashua, N. H., a corporation of Maine Application January 26, 1956, Serial No. 561,405

17 Claims. (Cl. 92--7) This invention relates to the continuous pulping of fibrous material, and more particularly, to novel apparatus and methods for advancing the solid particles of a solid-liquid mixture through said liquid independently of the movement of the liquid.

Pulping of wood or other fibrous material is carried out, for example, by digesting particles of fibrous materials such as wood chips in a highly heated liquid chemical solution preferably under pressure, as in the well known soda or sulfate processes for the manufacture of paper pulp. As another example, the digestion may also be carried out by steeping the fibrous materials at atmos pheric or sub-atmospheric pressure in cold liquid chemical solutions such as nitric acid or caustic. At the present time, such digestion in either case is usually carried out in batches, that is, a digester is filled with the raw material, such as wood chips, after which the chemical digester solution is admitted and suitable reaction conditions maintained for an interval of time sufficient to digest the wood chips. Thereafter, the batch of chips is discharged.

One of the major problems which must be solved in order to provide a continuous pulping process which would consist in continuously feeding the solid raw material, such as wood chips, into one end of the apparatus used for the digestion, and causing such raw material to move through said apparatus while admitting the heated chemical digester solution and finally discharging the material from the other end of the apparatus in the form of pulp, arises from the nature of the reacting mixture itself, that is, the mixture ofdiscrete particles in a liquid. It has proved to be most difficult to control the movement of such particles into a reacting vessel and through the liquid solution of chemicals to an outlet at the other end of the apparatus, since the particles are subject to both sticking and channelling which prevents the uniform movement essential for the production of pulp having uniform characteristics. Further difficulty arises in controlling the movement of the liquid, since it freely drains away from the mass of solid particles, making it impossible to use the liquid as a vehicle for carrying the solid particles through the apparatus.

Still another problem arises frm the tendency of the solid particles to plug up strainers and the like used to separate the solid particles from the liquid, particularly when they are mounted in an enclosed continuously op.- erating system.

According to the present invention, we have provided a novel apparatus for advancing the solid particles, such as wood chips, of a solid-liquid mixture through said liquid at a rate of movement substantially independent of the rate of movement of the liquid, and without sticking or channelling of said particles, as well as novel means and methods for compacting such solid particles and for causing limited reciprocatory relative movement between the solid particles and the liquid.

It is a feature of the invention that it is particularly adapted to aid in feeding solid particles suspended in a liquid into a reaction vessel, as well as for thereafter advancing such particles upwardly through such reaction vessel at a uniform rate to discharge at the other end thereof.

It is another feature of the invention that it is selfcleaning in operation, so that plugging difficulties do not arise even with continuously operating systems.

For the purpose of more fully explaining a preferred embodiment of the invention, reference is now made to the following specification, together with the accompanying drawings, wherein:

Fig. 1 is a diagrammatic view of a continuous pulping apparatus employing the particle advancing means of this invention;

Fig. 2 is an enlarged cross-sectional elevation showing a portion of the apparatus of Fig. 1 having therein the particle advancing means of this invention;

Fig. 3 is a plan view of the means of Fig. 2; and v Fig. 4 is an isometric view showing a portion of the means of Figs. 2 and 3.

Referring to the drawings, in Fig. 1 is shown a complete continuous pulping apparatus including a mixing vessel for suitably mixing and impregnating fibrous material such as wood chips with a liquid chemical solution such as a solution of soda ash to provide a solid particleliquid mixture or slurry. Such mixture is then pumped to the bottom of an upright pressurized reaction vessel of upwardly increasing cross-sectional area wherein the chips are treated by heating them under pressure in said solution as they are moved upwardly therethrough until they are discharged as a digested slurry at the top of the reaction vessel.

According to the present invention, novel foraminous solid particle lifting means mounted adjacent the entrance end of the vessel and extending throughout substantially the entire horizontal cross-sectional area adjacent the entrance end of said vessel closely adjacent the inner wall of said vessel, such as a perforated screw means, are provided for advancing and compacting the chips or other solid particle component of the solid particle-liquid mixture in an elongated mass or zone extending throughout the major portion of the length of the elongated pressurized reaction vessel at a rate substantially independent of the rate of movement of said liquid. Thus, the solid particle-liquid mixture may be fed into the reaction vessel, the mass of chips advanced therethrough through said zone at a uniform average rate without sticking or channelling and the digested chips then discharged to so provide uniform digestion as well as toprovide control of the degree of digestion by controlling the rate of advance. Since such rate of advance is substantially independent of the rate of movement of the liquid compo nent of the solid particle-liquid mixture because of the free movement of liquid through the lifting means, the liquid may be recirculated for heating it as desired. Ad-' ditionally, the chip advancing means may also act to cause a limited reciprocatory relative movement between the solid particles and the liquid, or additional means therefor may be provided if desired.

In more detail, the mixing or impregnating portion 0 the apparatus includes a suitable mixing vessel 12 partial-' ly filled with a suitable liquid chemical solution through its infeed pipe 14. Chips or other fibrous materials may be fed into the open top of mixing vessel 12 by any suitable means (not shown). A centrifugal pump 16 driven by any suitable means (not shown) is provided at the lower end of mixing vessel 12 for feeding themixture of chips and liquid from the mixing vessel into the pressurized reaction vessel.

The reaction portion of the apparatus includes a generally cylindrical upright elongated pressure vessel 22 of generally uniform cross-sectional area at least not de 3 creasing in its upward direction having a bottom safety valve 18 connected to pump 16 and a top discharge mechanism 26 connected to a suitable pulp storage tank (not shown). It is important that vessel 22 although of generally uniform cross-sectional area have a slight taper to provide a gradually increasing cross-sectional area, a taper of about /s inch of diameter per foot of length, for example, being suitable. A filter section 28 as well as a bottom outlet 29 may be provided in said vessel 22 for recirculation ofthe liquid component to heat it as desired. Any suitable heating means may be employed, for example, steam may be injected into the liquid to heatit.

As best shown in Figs. 2 through 4, the novel advancing means includes a foraminous screwmeans mounted for rotational and reciprocatory movement through a limited distance relatively to the length of the vessel within the reaction vessel 22 near the lower end thereof by means of a shaft 36 extending vertically through the bottom of said vessel generally axially thereof. More specifically, said foraminous screw means comprises a single turn helical plate 32 having therein a plurality of perforations 34' sufficient in number to allow substantially free passage of the liquid therethrough but of small enough size to prevent passage of the chips or other fibrous material. Furthermore, the step of such helical surface is closed by a fiat plate 36 extending vertically between its upper and lower edges 38 and 4t), and the peripheral edge thereof is positioned closely adjacent the inner walls of the reaction vessel 22 so that passage of chips into the bottom portion of said reaction vessel 22 may be prevented.

"For feeding the pressurized mixture of chips and liquid to the upper surface of said plate, a tubular member 42 having its inner wall concentric with and spaced from shaft 38 is mounted on the lower surface of said helical plate 32 extending downwardly therefrom, thus providing a central aperture 4-4 between the upper and lower radial edges 38 and it? respectively of said helical late and extending radially from said shaft to said memher in the lower portion of the helical surface near said lower edge 40. Said movable member 42 is positioned closely within a fixed tubular member 43 mounted in the lower end of reaction vessel 22 and extending both upwardly therefrom to overlap the downwardly extending edge of movable tubular member 442 and downwardly therefrom to provide a connection to inlet valve 24 through pipe 46, the lower end of said fixed member being provided with a suitable seal 48.

The lower end of shaft 3% extends into a hydraulic cylinder 50 mounted beneath the lower end of reaction vessel 22 and forms the piston thereof, said cylinder t) being provided with an inlet pipe 52 connected to a suitable source of fluid pressure to raise said shaft with the helical plate 32 to reciprocate said plate, the force of the vessel pressure against the area of the upper end of said Shaft being great enough to rapidly lower the plate when the pressure in cylinder 50 is exhausted, the pressure vesscl 22 in such circumstances acting as an accumulator to provide the necessary force at a rapid rate. Furthermore, the volume of liquid displaced by shaft 30 varies as the shaft reciprocates, causing the entire volume of liquid in vessel 22 to reciprocate over a limited distance. Suitable means (not shown) for alternately connecting pipe 52 to its source of pressure and to exhaust may be provided to reciprocate helical plate 32 at any desired rate. For rotating shaft 30 to rotate plate 32 in such direction as shown by the arrow in Fig. 2, a gear 54 is mounted on shaft 36 for reciprocatory movement relatively thereto as by a keyway, and is driven through a pinion 156 by a hydraulic motor 58 operated from a suitable source of pressure (not shown).

In operation, the solid particle-liquid mixture or slurry in mixing vessel 12 is fed into the reaction vessel 22 by centrifugal pump 16 so that it will be pressurized before entering said vessel. The mixture thus passes through safety valve 13, thence through the passageway formed between shaft 30 and tubular members 42 and 43, and finally outwardly through aperture 44 into the lower end of the reaction vessel 22 above the perforated helical plate 32. During a run, the reaction vessel is kept full of chips to maintain a compacted elongated mass or zone thereof, the individual chips moving slowly upwardly as they are reduced to pulp and discharged through mechanism 26 at the top of the reaction vessel.

During the feeding of the slurry into reaction vessel 22, the helical plate 32 is both rotated at a rate of say 6 revolutions per minute as shown by the arrow in Fig. 2 and reciprocated for a short distance axially thereof at a rate of say 12 strokes per minute as shown by the reference numeral 30a in Fig. 2 to provide an axial compo nent of movement of the chips fed through aperture 44 to move them upwardly to the bottom of the mass of chips in the reaction vessel and compact them thereon and advance them therethrough by exerting force only against the chips at the bottom end of said mass or zone.

Since the mass of chips fills the reaction vessel and its bottom extends downwardly toward the helical plate, such rotational and reciprocatory movement acts on the bottom of said mass of chips to advance it upwardly at a desired uniform average rate as Well as to compact it. The taper of the vessel makes it possible for the helical plate 32 to move the mass of chips upwardly without exerting extraordinarily high pressures on the chips, as too high pressures seriously damage the chips and cause a substantial reduction in the quality of the resulting pulp. The digested chips are discharged as pulp through mechanism 26 at the top of the machine while at the same time the mixture of chips and liquid is continuously fed into the bottom of the reaction vessel beneath the mass of chips through aperture 44. Preferably, the limited reciprocatory movement is arranged to function normally to successively advance the mass of chips, the rotational movement acting normally to feed the chips outward through aperture 44- below the mass of chips. This may be accomplished by arranging the hydraulic pressure on motor 58 so that it stalls when the rotating helical plate comes into firm contact with the mass of chips. Since the liquid component of the mixture passes freely through the perforations in helical plate 32 during such reciprocation or rotation, neither the reciprocatory nor rotational movement will affect the movement of the liquid so that the chips may be advanced independently thereof, except for the limited reciprocatory movement of the liquid caused by the reciprocation of shaft 30, which limited movement is valuable in that it aids the reaction by continuously washing away from the chips the material dissolved by the liquid chemical solution. Furthermore, the liquid may be continuously recirculated for heating or the like through filter 28 and inlet 29.

The upward movement of plate 32 due to the pressure in hydraulic cylinder 50 is relatively slow, occupying say of the total cycle, while the downward movement due to the pressure of the vessel acting on the end of shaft 30 is much more rapid, occupying but about 10% of the cycle. This is made possible by using the vessel in effect as a hydraulic accumulator. Such rapid downward movement forces the liquid under plate 32 to move rapidly. through the perforations 34, thus flushing away any solid particles that may have become lodged in the perforations 34.

Thus it will be seen that we have provided a novel means for advancing the solid particle component of a solid particle-liquid mixture independently of the liquid component thereof, as well as novel means and methods for compacting such solid particles and for causing lint ited reciprocatory relative movement between the solid particles and the liquid, so that we are, for example, enabled to provide a practical upflow continuous pulping apparatus for wood chips or other fibrous materials. Varvious modifications of the invention within the spirit thereof and the scope of the appended claims will occur to those skilled in this art.

We claim:

1. Continuous pulping apparatus for fibrous material comprising a generally upright pressurized reaction vessel of generally circular cross-sectional area for digesting said solid particles, means for feeding said mixture into the lower end of said reaction vessel and advancing the solid particle component thereof through said vessel substantially independently of the movement of said liquid in said vessel including a single turn helical screw having a perforated surface extending generally in a horizontal plane across substantially the entire cross-sectional area of said vessel for free passage of said liquid therethrough while preventing passage of said particles and having a central opening for passage of said solid particle-liquid mixture therethrough, pump means for feeding pressurized solid particle-liquid mixture into said vessel adjacent to and in advance of said surface, and means for rotating and reciprocating said screw to advance said particles upwardly, and discharge means for discharging the digested solid particle component from the upper end of said reaction vessel.

2. Apparatus for treating the solid particle component of a solid particle-liquid mixture comprising a generally upright elongated vessel and means for feeding said mixture into said vessel adjacent the lower end thereof and advancing the solid particle component thereof upwardly through said vessel substantially independently of the movement of said liquid in said vessel, including a solid particle lifting member mounted adjacent the lower end of said vessel for generally vertical reciprocatory movement, said member having a foraminous surface extending generally ina horizontal plane across substantially the entire cross-sectional area of said vessel with its outer periphery closely adjacent the inner walls of said vessel for free passage of said liquid therethrough while preventing passage of said particles, means for feeding solid particle-liquid mixture into said vessel adjacent to and in advance of said surface, and means for reciprocating said member through a limited distance relatively to the length of said vessel to advance said particles upwardly by exerting lifting force directly only on particles located adjacent the lower end of said vessel in advance of said lifting member to progressively compact said particles and to advance the mass of said particles progressively upwardly through said vessel while permitting free movement of liquid through said lifting member.

3. Apparatus as claimed in claim 2 wherein said vessel has an increasing cross-sectional area in the direction of advance of said solid particles.

4. Apparatus as claimed in claim 2 wherein said foraminous means comprises a foraminous screw means.

5. Apparatus as claimed in claim 4 further including means for rotating said screw means.

6. Continuous pulping apparatus for solid particleliquid mixtures comprising a generally upright elongated pressurized reaction vessel of generally circular cross-sectional area for digesting said solid particles, means for feeding said mixture into said reaction vessel adjacent the lower end thereof and advancing the solid particle component thereof upwardly through said vessel substantially independently of the movement of said liquid in said vessel, including a solid particle lifting member mounted adjacent the lower end of said vessel for generally vertical reciprocatory movement, said member having a foraminous surface extending generally in a horizontal plane across substantially the entire cross-sectional area of said vessel with its outer periphery closely adjacent the inner walls of said vessel for free passage of said liquid therethrough while preventing passage of said particles, pump means for feeding pressurized solid particle-liquid mixture into said vessel adjacent to and in advance of said surface, means for reciprocating said member through a limited distancerelatively to the length of said vessel'to advance said particles upwardly by exerting lifting force directly only on particles located adjacent the lower end of said vessel in advance of said lifting member to progressively compact said particles and to advance the mass of said particles progressively upwardly through said vessel while permitting free movement of liquid through said lifting member, and discharge means for discharging the digested solid particle component from the upper end of said reaction vessel.

7. Continuous pulping apparatus as claimed in claim 6 wherein said means for reciprocating downwardly said means for feeding and advancing includes said pressure vessel acting as an accumulator.

8. Continuous pulping apparatus as claimed in claim 6 wherein said member includes a perforated single turn helical surface having its outer periphery closely adjacent the inner walls of said pressure vessel, the step of said helical surface having a plate extending from the outer periphery thereof toward the center thereof and having a central opening for feeding said pressurized solid particle-liquid mixture, and means for feeding said mixture from said pump means to said central opening,

9. Continuous pulping apparatus for fibrous material comprising a mixing vessel for combining said fibrous material with a liquid to form a solid particle-liquid mixture, a generally upright pressurized reaction vessel of generally circular and upwardly increasing cross-sectional area for digesting said fibrous material, means for feeding said mixture from said mixing vessel into the lower end of said reaction vessel and advancing the solid particle component thereof through said vessel substantially independently of the movement of said liquid in said vessel including a single turn helical screw having a perforated surface for free passage of said liquid therethrough while preventing passage of said particles and having a central opening for passage of said solid particle-liquid mixture therethrough, pump means for feeding pressurized solid particle-liquid mixture from said mixing vessel through said central opening, and means for rotating and reciprocating said screw to advance said particles upwardly, and discharge means for discharging the digested solid particle component from the upper end of said reaction vessel.

10. Continuous pulping apparatus for solid particleliquid mixtures comprising a generally upright pressurized reaction vessel for digesting said solid particles, means mounted within said vessel for causing limited reciprocatory relative movement between said solid par ticles and said liquid including piston means extending through a wall of said vessel, and means for reciprocating said piston means to vary the enclosed volume of said vessel to cause said relative movement between said liquid and said particles, and discharge means for discharging the digested solid particle component from the upper end of said reaction vessel.

11. Apparatus for the continuous treatment of the solid particle component of a solid-particle-liquid mixture in an upwardly arranged elongated reaction vessel having a generally uniform cross-sectional area at least not decreasing in its upward direction by feeding substantially continuously said mixture into said reaction vessel adjacent the lower entrance end thereof to maintain a compacted mass of said solid particles within an elongated zone in the central and opposite upper end portions thereof, advancing the solid particle component thereof upwardly through said zone at a rate substantially independent of the movement of liquid in said vessel to treat said solid particles, meanwhile treating the same, and substantially continuously discharging said treated solid particles from said opposite upper end of said vessel, comprising foraminous solid particle lifting means mounted adjacent the entrance end of said vessel and extending throughout substantially the entire horlzontal cross-sectional area adjacent said entrance end of asset is said vessel with its outer periphery closely adjacent the inner walls of said vessel and means for operating said lifting means to feed said solid particle component to the entrance end of said zone and to exert lifting force directly only on particles located at the entrance end of said zone to progressively compact said particles and to advance the mass of said particles progressively upwardly through said zone while permitting free movement of liquid through said lifting means.

12. Apparatus for the continuous treatment of the wood chip component of a wood chip liquid mixture in an elongated, generally upright pressurized reaction vessel of generally uniform and gradually increasing cross-sectional area throughout the major portion of its length at least not decreasing in cross-sectional area in its upward direction by feeding substantially continuously said mixture into said reaction vessel adjacent the lower entrance end thereof to maintain a compacted mass of said wood chips within an elongated zone in the central and upper portion thereof filling its entire cross-sectional area, advancing the wood chip component thereof upwardly through said zone at a rate substantially independent of the movement of liquid in said vessel to treat said wood chips, meanwhile treating the same, and substantially continuously discharging said treated wood chips from the upper end of said vessel, comprising foraminous piston wood chip lifting means mounted adacent the lower end of said vessel for generally vertical reciprocatory movement and extending generally in a horizontal plane across substantially the entire crosssectional area of said vessel with its outer periphery closely adjacent the inner walls of said vessel for free passage of said liquid therethrough while preventing passage of said wood chips, means for feeding wood chip liquid mixture into said vessel adjacent to and in advance of said piston means, means for reciprocating said piston through a limited distance relatively to the length of said vessel to advance said wood chips into contact with wood chips at the lower end of said zone and to exert lifting force directly only on particles located at the entrance end of said zone to progressively compact said wood chips at the lower end of said zone and to advance the mass of wood chips progressively upwardly throughout the length of said zone while permitting free movement of liquid through said lifting means, and discharge means for discharging the digested wood chips from the upper end of said zone at the upper end of said reaction vessel.

13. Apparatus for the continuous treatment of the wood chip component of a wood chip-liquid mixture as claimed in claim 12 further including means for recirculating liquid through said wood chips in said compacted zone in a direction independent of the direction of advance of said wood chips throughout said zone.

14. A method for the continuous treatment of the wood chip component of a wood chip-liquid mixture to treat said wood chip component with a liquid comprising continuously maintaining a mass of said wood chips in a generally upright elongated compacted pressurized zone of substantially uniform cross-sectional area throughout its length at least not decreasing in cross-sectional area in its upward direction by progressively feeding said wood chips to the lower end of said zone, and compacting them thereat, progressively advancing said wood chips throughout the length of said zone meanwhile simultaneously treating the same during said advancing by fluid movement through said compacted wood chips at a rate independent of the rate of advance of said wood chips by successively contacting and pressing against wood chips only at the lower end of said zone across substantially the entire said cross-sectional area thereof and continuously discharging the treated wood chips from the upper end of said zone meanwhile maintaining the pressure therein.

15. A method as claimed in claim 14 wherein limited reciprocatory relative movement is caused between said wood chips and said liquid.

16. A method as claimed in claim 14 wherein said zone is pressurized to a high pressure.

17. A method as claimed in claim 14 wherein said zone gradually increases in cross-sectional area in the direction of advance of said wood chips.

References Cited in the file of this patent UNITED STATES PATENTS 71,728 Ficklen Dec. 3, 1867 616,033 Sturcke Dec. 13, 1898 688,050 Zeyen et a1. Dec. 3, 1901 797,374 Roberts p Aug. 15, 1905 896,473 Shortt Aug. 18, 1908 899,961 Edgerton Sept. 29, 1908 1,461,614 Harrison July 10, 1923 1,915,812 Wollenberg June 27, 1933 1,991,245 De La Roza Feb. 12, 1935 2,138,455 Kreissler Nov. 20, 1938 

1. CONTINUOUS PULPING APPARATUS MATERIAL COMPRISING A GENERALLY UPRIGHT PRESSURIZED REACTION VESSEL OF GENERALLY CIRCULAR CROSS-SECTIONAL AREA FOR DISGESTING SAID SOLID PARTICLES MEANS FEEDING SAID MIXTURE INTO THE LOWER END OF SAID REACTION VESSEL AND ADVANCING THE SOLID PARTICLE COMPONENT THEREOF THROUGH SAID VESSEL SUBSTANTIALLY INDEPENDENTLY OF THE MOVEMENT OF SAID LIQUID IN SAID VESSEL INCLUDING A SINGLE TURN HELICAL SCREW HAVING A PERFORATED SURFACE EXTENDING GENERALLY IN A HORIZONTAL PLANE ACROSS SUBSTANTIALLY THE ENTIRE CROSS-SECTIONAL AREA OF SAID VESSEL FOR FREE PASSAGE OF SAID LIQUID THERETHROUGH WHILE 